1. Field of the Invention
This invention relates to a method of detecting a forgery such as a counterfeit ticket or a forged ticket made by copying a genuine ticket. In addition, this invention relates to an apparatus for detecting a forgery. Furthermore, this invention relates to a recording medium which stores a signal representing a computer program for detecting a forgery.
2. Description of the Related Art
According to a known forgery detecting system, genuine tickets have prints using special ink such as magnetic ink which differs from toner employed in usual copying machines. Copying such a genuine ticket by a usual copying machine generates a forged ticket. The forged ticket has a picture portion which is a photo-copy of the special-ink-based print on the genuine ticket, but which is made of the toner rather than the special ink. The forged ticket can be discriminated from genuine tickets by a detecting device provided with a sensor for the special ink. The detecting device determines whether or not every subject ticket has the special ink. A subject ticket which has the special ink is concluded to be genuine. On the other, a subject ticket which lacks the special ink is concluded to be counterfeit.
A forged ticket which is made by the above-mentioned copying process is referred to as a first forged ticket. A second forged ticket can be made by sticking a special-ink-containing paper fragment on a first forged ticket. The detecting device in the known forgery detecting system fails to discriminate the second forged ticket from genuine tickets.
Japanese published unexamined patent application 10-232911 discloses a prepaid card on which a two-dimensional code is printed. The prepaid card in Japanese application 10-232911 can be provided with a hole or holes in the area of the two-dimensional code. The two-dimensional code represents first information. The position of the hole or the positions of the holes represent second information. After a virgin card is made, such a hole or holes can be provided at arbitrary positions of the card by a punching process. Therefore, the second information can be updated at any time.
Japanese application 10-232911 also discloses a system for discriminating an illegal card from a legitimate prepaid card. In the system of Japanese application 10-232911, prepaid cards have magnetic portions respectively. During the issue of every prepaid card, data representing an amount of money and data inherent to the card (card ID data) are shuffled into first encryption-resultant data, and the first encryption-resultant data are recorded on the magnetic portion thereof. In addition, the card ID data are encoded into second encryption-resultant data. A two-dimensional code representing the second encryption-resultant data is printed on the card by using invisible ink. Furthermore, a hole or holes are punched through the card in response to the first encryption-resultant data. Specifically, the position of the hole or the positions of the holes represent the first encryption-resultant data. The hole or holes are in the area of the two-dimensional code. The hole or holes may be located around the area of the two-dimensional code.
The system of Japanese application 10-232911 implements a card check process as follows. A signal is magnetically read out from the magnetic portion of a subject card. Signals are optically read out from the two-dimensional code and the hole or holes in the subject card. The signal read out from the magnetic portion is decoded into first money-amount data and first card ID data. The signal read out from the two-dimensional code is decoded into second card ID data. The signal read out from the hole or holes is decoded into second money-amount data and third card ID data. The first card ID data, the second card ID data, and the third card ID data are collated with each other. In addition, the first money-amount data and the second money-amount data are collated with each other. The results of these collations are used in deciding whether the subject card is legitimate or illegal.
It is a first object of this invention to provide an improved method of detecting a forgery.
It is a second object of this invention to provide an improved apparatus for detecting a forgery.
It is a third object of this invention to provide a recording medium which stores a signal representing an improved computer program for detecting a forgery.
A first aspect of this invention provides a method of determining whether or not a medium on which a two-dimensional code and a predetermined figure pattern are printed is counterfeit, wherein an error in the two-dimensional code is correctable during decoding of the two-dimensional code, and a cell position corresponding to a position of the error is detectable, the predetermined figure pattern being made of special ink, the two-dimensional code and the predetermined figure pattern overlapping each other at a specified place in the medium. The method comprises the steps of optically reading the two-dimensional code from the medium; decoding the two-dimensional code which has been optically read; in cases where error correction is executed during the decoding of the two-dimensional code, detecting an error correction position corresponding to a cell position having a related error; determining whether or not the detected error correction position is in the specified place; and judging whether or not the medium is counterfeit in response to a result of the determining.
A second aspect of this invention is based on the first aspect thereof, and provides a method wherein cells composing the two-dimensional code are grouped into blocks, and arrangement information representing arrangement of the cells in the blocks is recorded in the two-dimensional code and the error correction position is detected on the basis of the arrangement information.
A third aspect of this invention is based on the first aspect thereof, and provides a method wherein the error-correction-position detecting step comprises comparing a bright-dark cell pattern indicated by cells regenerated on the basis of results of the decoding of the two-dimensional code and information of a recording format of the two-dimensional code with a bright-dark cell pattern indicated by the optically-read two-dimensional code; and detecting the error correction position in response to a result of the comparing.
A fourth aspect of this invention is based on the first aspect thereof, and provides a method further comprising causing a sensor to scan the specified place, the sensor being able to sense the special ink; determining whether the special ink is present in or absent from the specified place in response to an output signal of the sensor; and concluding the medium to be counterfeit when it is determined that the special ink is absent from the specified place.
A fifth aspect of this invention provides an apparatus for determining whether or not a medium on which a two-dimensional code and a predetermined figure pattern are printed is counterfeit, wherein an error in the two-dimensional code is correctable during decoding of the two-dimensional code, and a cell position corresponding to a position of the error is detectable, the predetermined figure pattern being made of special ink, the two-dimensional code and the predetermined figure pattern overlapping each other at a specified place in the medium. The apparatus comprises reading means for optically reading bright-dark conditions of respective cells composing the two-dimensional code on the medium; decoding means for decoding the two-dimensional code on the basis of the optically-read bright-dark conditions of the cells; error-correction-position detecting means for, in cases where error correction is executed during the decoding of the two-dimensional code, detecting an error correction position corresponding to a cell position having a related error; determining means for determining whether or not the detected error correction position is in the specified place; and judging means for judging whether or not the medium is counterfeit in response to a result of the determining by the determining means.
A sixth aspect of this invention is based on the fifth aspect thereof, and provides an apparatus wherein cells composing the two-dimensional code are grouped into blocks, and arrangement information representing arrangement of the cells in the blocks is recorded in the two-dimensional code, and wherein the error-correction-position detecting means comprises means for detecting the error correction position on the basis of the arrangement information.
A seventh aspect of this invention is based on the fifth aspect thereof, and provides an apparatus wherein the error-correction-position detecting means comprises comparing means for comparing a bright-dark cell pattern indicated by cells regenerated on the basis of results of the decoding of the two-dimensional code and information of a recording format of the two-dimensional code with a bright-dark cell pattern indicated by the optically-read two-dimensional code; and detecting means for detecting the error correction position in response to a result of the comparing.
An eighth aspect of this invention is based on the fifth aspect thereof, and provides an apparatus further comprising at least one host and a plurality of terminals, wherein the reading means, the decoding means, and the error-correction-position detecting means are provided in the terminals, and wherein the determining means and the judging means are provided in the host, and the terminals inform the host of the error correction position.
A ninth aspect of this invention is based on the seventh aspect thereof, and provides an apparatus further comprising at least one host and a plurality of terminals, wherein the reading means and the decoding means are provided in the terminals, wherein the error-correction-position detecting means, the determining means, and the judging means are provided in the host, wherein the terminals notify the host of the results of the decoding and the information of the recording format of the two-dimensional code.
A tenth aspect of this invention is based on the fifth aspect thereof, and provides an apparatus further comprising a sensor for sensing the special ink; means for causing the sensor to scan the specified place; means for determining whether the special ink is present in or absent from the specified place in response to an output signal of the sensor; and means for concluding the medium to be counterfeit when it is determined that the special ink is absent from the specified place.
An eleventh aspect of this invention provides a recording medium loaded with a computer program corresponding to the method in one of the first to fourth aspects of this invention.
A twelfth aspect of this invention provides an apparatus comprising first means for capturing an image of a two-dimensional code on a subject, the two-dimensional code containing error correction information; second means for decoding the two-dimensional code in response to the image captured by the first means while correcting an error in the two-dimensional code in response to the error correction information and generating a signal representing a position of the error relative to an area of the two-dimensional code; and third means for determining whether the subject is genuine or counterfeit in response to the error position represented by the signal generated by the second means.
A thirteenth aspect of this invention provides an apparatus comprising first means for capturing an image of a two-dimensional code on a subject, the two-dimensional code containing error correction information; second means for decoding the two-dimensional code in response to the image captured by the first means while correcting an error in the two-dimensional code in response to the error correction information and generating a signal representing a position of the error relative to an area of the two-dimensional code; third means for determining whether or not the error position represented by the signal generated by the second means coincides with a specified position in the area of the two-dimensional code; fourth means for concluding the subject to be counterfeit when the third means determines that the error position coincides with the specified position; and fifth means for concluding the subject to be genuine when the third means determines that the error position does not coincide with the specified position.